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W J Huk

Publications and source records attributed to W J Huk.

At least 55 records · Page 3Linked to original sources
PubMed1991

The neocortico to mesio-basal limbic propagation of focal epileptic activity during the spike-wave complex.

In order to localize epileptogenic electrophysiological sources, a multichannel MEG system was used in 3 patients with partial epilepsy during presurgical evaluation. MEG and EEG (including scalp, sphenoidal and intracranial foramen ovale electrodes) were recorded simultaneously during a period of intensive video-EEG monitoring in order to observe single spontaneous spikes. In addition to MRI, SPECT and PET investigations were performed. Electrical activity subsequent to the activity of the epileptic focus could be localized by the MEG after noise reduction using a temporal correlation technique. Simultaneous registration of the magnetic field and the electrical field showed that the source of the primary focal epileptic activity (first period during the total spike wave complex where a dipolar magnetic field pattern is found) is localized in neocortical lateral regions, whereas another focal epileptic activity in a later phase of propagation occurs in temporal mesial regions. In 1 patient (case 1) the primary focal epileptic activity was localized in the surrounding neocortical tissue of an angioma and the middle and inferior temporal gyrus. The second phase of propagation is localized in temporo-basal-mesial regions, including para- and hippocampal structures. The latest center of activity occurred in posterior parts of the gyrus cinguli. In 2 other patients, the primary focal epileptogenic activity was localized at the insula and also spread into temporal basal mesial regions. A multi-modal approach to research of focal epilepsy, combining metabolic, electrical potential, magnetoencephalographic and morphological data, recorded by non-invasive techniques, offers new perspectives for the detection of involved brain regions. The 3-D and time-resolved localization of focal epileptic activity, correlated with the individual anatomy of the human brain, may improve the determination of neuronal populations involved in the individual epileptogenic process, especially in the interaction between temporal or extratemporal neocortex and limbic system.

Adult↗
PubMed1991

[In-vitro-study and patient examinations with MRT: the significance of metal implants].

This study presents the results of in-vitro and clinical experiences with metallic implants during MRT investigations. In-vitro temperature measurements of various implants showed little temperature rise depending on the shape and the orientation in the static magnetic field (max. 0.3 degrees C). Ferromagnetic forces could not be detected with these implants. In contrast, severe temperature increase (9.4 degrees C) was observed with an intratracheal spiral tube. Tubes of this type should not be used in MR imaging to avoid the risk of burning. 105 MR examinations were performed in patients with metallic implants (CNS shunts, aortocoronary bypass grafts, aortic-, mitral-prosthesis, orthopedic implants, skin staples, shrapnels). Patients with vascular clips were accepted for MR imaging when the clips were non-ferromagnetic only. No adverse effects were observed in these patients.

Ferric Compounds↗
PubMed1990

Regional cerebral blood flow during focal seizures of temporal and frontocentral onset.

Ictal single photon emission computed tomography recordings were performed in 9 patients in the course of 11 seizures. Injections of radionuclide were made an average of 72 seconds after the onset of the seizure as indicated by electroencephalography. All patients also underwent interictal recordings. In 6 patients, the localization of the electroencephalographic focus and the morphological lesions corresponded with the ictal hyperperfusion. This could be seen in single photon emission computed tomography. Seizures triggered by hyperventilation, and seizures of patients with anatomical brain lesions (e.g., cysts, surgical defects, and recent injections of technetium-hexamethylene-propylene-amine-oxime) showed an absent or noncorresponding localization of the ictal recording. The ictal and interictal recording seems suitable as a confirmatory noninvasive method for the localization of the epileptogenic focus, particularly in the preoperative evaluation of epilepsy.

Adolescent↗
PubMed1990

Zieve's syndrome and intracranial haemorrhage: coincidence or related disorders.

Zieve's syndrome (hyperlipidaemia, anaemia and fatty liver degeneration) may rarely occur with intracranial haemorrhage. Four patients suffering from both diseases are reported. Although it remains unclear whether there is a causal relationship between the two, it seems that hyperlipidaemia may be a major cause of intracranial bleeding. One reason for the small number of reported cases may be that hyperlipidaemic serum levels rapidly decrease after alcohol withdrawal.

Adult↗
PubMed1990

Magnetic source localization in focal epilepsy. Multichannel magnetoencephalography correlated with magnetic resonance brain imaging.

Initial results of magnetic source localization by means of multichannel recording using a 10 or a 31 channel system are reported. Simultaneous magnetoencephalographic (MEG) and electroencephalographic (EEG) (scalp, sphenoidal and foramen oval) recording, as well as magnetic resonance imaging (MRI) with a fixed head position, permits the projection of brain structures and the source localized from MEG into a three-dimensional coordinate system. From 8 patients investigated it can be clearly seen that the method is of diagnostic relevance for patients with temporal lobe epilepsy. Results are demonstrated for 3 patients with interesting findings concerning the anatomical correlation with source localization. The findings indicate that MRI-correlated magnetic source localization by means of multichannel recordings provides important advantages in epilepsy research. (1) Increased precision permits noninvasive localization. Deeper sources in the temporal lobe are localized from MEG combined with scalp or minor invasive EEG. (2) Investigation time is considerably shortened. (3) Single events can be localized for supplementary presurgical information concerning the three-dimensional anatomical localization of focal epileptic activity in the brain.

Adult↗
PubMed1990

Diagnostic significance of flow separation within the carotid bifurcation demonstrated by digital subtraction angiography.

The presence of an area of reversed blood flow due to flow separation in the interval carotid artery is a normal finding in Doppler ultrasound studies in vivo as well as in model carotid bifurcations. This flow separation phenomenon is caused by the geometry of the carotid bifurcation and the fluid dynamics of blood. We demonstrated the flow separation phenomenon on lateral-projection intra-arterial digital subtraction angiograms in 99 of 100 carotid bifurcations. The mean duration of flow separation was 5.8 seconds, with values up to 14 seconds in normal carotid bifurcations. The presence of this flow separation phenomenon is almost independent of atherosclerotic lesions and is not correlated with cerebral ischemia. Therefore, the angiographic finding of a flow separation has no diagnostic value. However, our results refer to a factor that may be important in the genesis of atherosclerosis at the carotid bifurcation, namely the duration of the stay of blood and its components within the area of flow separation.

Adult↗
PubMed1989

CT, MRI and SPECT neuroimaging in status epilepticus with simple partial and complex partial seizures: case report.

A 35-year-old female patient suffering from epilepsy was examined during status epilepticus with simple partial and complex partial seizures by means of EEG, CT, MRI and ictal SPECT. All these examinations showed focal abnormalities with identical location due to oedema and hypervascularisation; these were, however, absent during examinations carried out before and after status epilepticus.

Adult↗
PubMed1987

Intrasphenoidal encephaloceles--a clinical entity.

In the current classification basal encephaloceles are grouped together with real transsphenoidal encephaloceles. But those encephaloceles extending only into but not through the sphenoid sinus seem to represent a specific clinical entity and therefore should be regarded as a rare subgroup of sphenoidal encephaloceles. One personal case and six cases from the literature are reviewed, the own case being associated with an empty sella turcica. The initial sign is rhinorrhea, almost invariably. The association with other intracranial anomalies is uncommon. The extradural transsphenoidal or transethmoidal midline approach accompanied by a shunting procedure today is the most suitable method of surgical treatment.

Adult↗
PubMed1987

[Diagnostic imaging in spinal tumors].

In addition to noninvasive imaging procedures, conventional radiology and isotope scintigraphy, computed tomography (CT) and magnetic resonance imaging (MRI) are also now available for the diagnosis of tumors of the spinal column. For specific problems, invasive methods like myelography and angiography are still indicated. The latter serves at the same time as an access for therapeutic endovascular procedures (i.e., embolization), which are mostly necessary preoperatively in highly vascular tumors. The diagnostic value of individual methods is discussed. For the invasive procedures, the risks are discussed and recommendations are made to avoid complications.

Diagnosis, Differential↗
PubMed1985

Nuclear magnetic resonance imaging of the region of the sella turcica.

Nuclear magnetic resonance (NMR) imaging is a versatile technique which has proved more sensitive in the detection of perisellar lesions than CT. A multiplanar facility, the demonstration of blood flow, and the lack of bone artefacts are its main advantages in this respect. Limitations are seen in its inability to identify small calcifications and to distinguish clearly perifocal oedema and tumour especially in malignant lesions. Relatively thick slices of 5-10 mm make the detection of microadenomas very difficult, mainly because of partial volume effects. T1 and T2 values alone are not sufficient to provide specific diagnosis. No reliable criteria have been determined yet, which would indicate the quality of pathological involvement of peritumorous structures by tumours of the sella region. At present NMR still plays a more complementary role to CT in the evaluation of this complex anatomical area. We are confident that with future technical refinements NMR will be able to replace ionizing radiation for the diagnostic imaging of the sella.

Adenoma↗
PubMed1984

Magnetic resonance imaging (MRI): method and early clinical experiences in diseases of the central nervous system.

Magnetic resonance imaging (MRI) has undergone a rapid development which is still continuing. In this article a survey is given of the present status of this new diagnostic tool in the evaluation of diseases of the central nervous system. When atoms with uneven numbers of protons or neutrons in a homogeneous magnetic field are tilted against the main vector of this field by a radiofrequency pulse, nuclear magnetic resonance can be observed. During the relaxation of the little dipoles back to the direction of the underlying magnetic field, a resonance signal is generated. The superposition of variable field gradients enables the scanning of sectional images in the axial, frontal and sagittal plane. The variables of H+-magnetic resonance which can be utilized for imaging are: the proton density, the relaxation times T1 (spin-lattice) and T2 (spin-spin) and flow effects. While the proton density in organic tissue fluctuates only by some 10%, the relaxation times may vary by several hundred per cent. Tissue contrast, therefore, is mainly based on relaxation times differences. The image character can also be influenced by variations of imaging parameters (i.e. repetition rate, interpulse delay, read out or echo delay) in different imaging sequences, such as the spin-echo and the inversion recovery technique. Depending on these imaging parameters T1 and T2 will contribute to the signal to a varying degree. This fact is most important for the diagnostic information of MRI. In initial clinical experiences in the diagnosis of diseases of the central nervous system, MRI has demonstrated high sensitivity in the detection of lesions (such as oedema, neoplasms, demyelinating disease), but less significance in lesion discrimination. In spinal disease the direct sagittal imaging of MRI enables MRI-myelography without contrast medium, superior to conventional myelography in many cases. For detailed evaluation of disc disease, however, the spatial resolution still has to be improved. Promising results have been obtained from flow effects. Depending on the flow velocity of blood, vessels appear white with intensive signals (slow flow) or black due to low signal intensities (rapid flow). MRI-angiography including measurement of blood flow seems possible. MRI-contrast media are not yet available for routine clinical use. Promising results have been reported on the basis of rare-earth elements, such as gadolinium Gd3+. These substances decrease T1 and T2 with subsequent increase in signal intensity. Concerning harmful side-effects of MRI, three possible sources have to be considered: the static magnetic field, the changing magnetic field, and radiofrequency heating.(ABSTRACT TRUNCATED AT 400 WORDS)

Adenoma↗
PubMed1983

[Computer tomographically guided stereotactic interstitial therapy of brain tumors using temporary or permanent 125iodine seed implantation].

Therapy resistance of inoperable malignant gliomas is an unsolved problem for radiotherapy. A combination of interstitial therapy and percutaneous high voltage therapy is described which should improve the prognosis of brain tumours when it has been perfected. For all tumours of low malignancy we recommend the permanent implantation of 125iodine seeds of low activity (10-60 mCi 125I, DO = 6-10 rad/h.) as the primary form of treatment, possibly supplemented by high voltage therapy. For tumours of higher malignancy, temporary implantation of high activity 125I is indicated (more than 200 mCi, DO = 25-100 rad/h.) as local boost before or after total volume irradiation of brain. Our experience of 30 patients up to date is encouraging.

Adult↗
PubMedDate not supplied

Echo-planar imaging of the central nervous system at 1.0 T.

Echo-planar imaging (EPI) on the authors' 1-T prototype imager provides high-quality 100-msec images of the central nervous system. Contrast parameters can be chosen freely. Three-dimensional EPI sequences provide isotropically resolved data sets with 1-mm resolution. Brain perfusion and blood-brain barrier disruption can be assessed in time-course studies with gadopentetate dimeglumine. The current state of development of the authors' midfield research EPI system is discussed and its image quality illustrated through selected patient studies.

Blood-Brain Barrier↗
PubMedDate not supplied

Ictal and interictal activity in partial epilepsy recorded with multichannel magnetoelectroencephalography: correlation of electroencephalography/electrocorticography, magnetic resonance imaging, single photon emission computed tomography, and positron emission tomography findings.

Ictal and interictal epileptic activity was recorded for the first time by multichannel magnetoencephalography (MEG) in three patients with partial epilepsy. Pre- and intra-operative localization of the epileptogenic region was compared. The interictal epileptic activity was localized at the same region of the temporal or frontal lobe as the ictal activity. Main zones of ictal activity were shown to evolve from the tissue at the centers of interictal activity. Pre- and intra-operative electrocorticography (ECoG) as well as postoperative outcome confirmed localization in the temporal and frontal lobe. Results also correlated with findings from scalp EEG, interictal and ictal single photon emission computed tomography (SPECT), positron emission tomography (PET), and magnetic resonance imaging (MRI). Combined multichannel MEG/EEG recording permitted dipole localization of interictal and ictal activity.

Adult↗
PubMedDate not supplied

Virtual labyrinthoscopy: visualization of the inner ear with interactive direct volume rendering.

Computed tomography (CT) is the modality of choice for detailed imaging of the bony labyrinth. Usually, information about the complex three-dimensional anatomic structures of the inner ear is presented as two-dimensional section images. Interactive direct volume rendering is a powerful method for visualization of the labyrinth. Unlike other visualization methods, direct volume rendering enables direct visualization of the bony labyrinth without explicit segmentation prior to the visualization process. Direct volume rendering was applied to visualization of the structures of the temporal bone in five patients without pathologic conditions and four patients with pathologic conditions. In all cases, clear representations of the bony labyrinth and the facial canal were provided. Because standard CT examinations combined with interactive visualization based on direct volume rendering are used, the method is fast and flexible. Therefore, this approach is applicable in routine clinical work. Problems occur in patients with effusion in the temporal bone because adjustment of imaging parameters for proper delineation of the target structures is difficult in this situation. However, direct volume rendering can produce meaningful images of high quality even in these problematic cases. The term virtual labyrinthoscopy is suggested for visualization of the labyrinth by using direct volume rendering.

Cochlea↗
PubMedDate not supplied

Local and remote visualization techniques for interactive direct volume rendering in neuroradiology.

The increasing capabilities of magnetic resonance (MR) imaging and multisection spiral computed tomography (CT) to acquire volumetric data with near-isotropic voxels make three-dimensional (3D) postprocessing a necessity, especially in studies of complex structures like intracranial vessels. Since most modern CT and MR imagers provide limited postprocessing capabilities, 3D visualization with interactive direct volume rendering requires expensive graphics workstations that are not available at many institutions. An approach has been developed that combines fast visualization on a low-cost PC system with high-quality visualization on a high-end graphics workstation that is directly accessed and remotely controlled from the PC environment via the Internet by using a Java client. For comparison of quality, both techniques were applied to several neuroradiologic studies: visualization of structures related to the inner ear, intracranial aneurysms, and the brainstem and surrounding neurovascular structures. The results of pure PC-based visualization were comparable with those of many commercially available volume-rendering systems. In addition, the high-end graphics workstation with 3D texture-mapping capabilities provides visualization results of the highest quality. Combining local and remote 3D visualization allows even small radiologic institutions to achieve low-cost but high-quality 3D visualization of volumetric data.

Brain Diseases↗